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Fish

We monitor fish communities because they serve as environmental indicators of river and stream health.

PWD scientists with striped bass collected from Schuylkill River.

Overview

Philadelphia's rivers and streams contain fish of all shapes and sizes, from small minnows to huge striped bass and carp. Large game fish such as bass are at the top of the food chain and cannot survive without clean water, good habitat, and the right types and amounts of food. Many of Philadelphia's rivers and streams have fair to good water quality, but fish communities are negatively affected by stormwater and habitat destruction as well as adverse changes to the variety of insect food available.

Fish Monitoring

We collect fish with electrofishing equipment according to protocols recommended by EPA, USGS, and PADEP. An electrical current is applied to the water, briefly stunning the fish so that they can be scooped up with nets. The fish are then measured and checked for any external signs of disease, injury or stress, then returned to the stream. Depending on site conditions, PWD uses backpack, tote barge, and boat mounted electrofishing equipment. Most stream assessment surveys are conducted with Rapid Bioassessment Protocols (RBPs) from USEPA, described briefly within this section. For more information, refer to the USEPA guidance documents, linked below under Additional Resources

Migratory Fish Passage Restoration and Monitoring

Philadelphia was once home to very large spawning runs of American shad and other anadromous fish (fish that live in the ocean much of their lives but ascend rivers and streams to spawn in fresh water). The Philadelphia region is also home to the American eel, a catadromous fish (fish that spend most of their lives in fresh or brackish water and spawn in the ocean). While many other native fish may move around within the Delaware estuary and Philadelphia’s freshwater tributaries, shad are the primary focus of PWD’s monitoring efforts.

Fish Migration Assessments

We partner with the Pennsylvania Fish and Boat Commission (PFBC) in tracking restoration of our native migratory fish populations. When migratory fish are expected to be in the rivers, PWD aquatic biologists use electrofishing equipment to estimate their abundance. When anadromous fish are collected, a small number may be sacrificed so that biologists from the PFBC can examine them for hatchery tags. These tags are located in the fish’s otolith (ear bone) and can indicate a fish’s age as well as whether the fish was raised at a hatchery or is part of a naturally reproducing population. Over time, the ratio of hatchery-raised fish to natural fish in these subsamples can provide information about whether the population is increasing on its own.

Documents

PWD aquatic biologists Joe Perillo and Lance Butler published results of fish monitoring trends in the Schuylkill River from 2002-2006 in the Journal of the Pennsylvania Academy of ScienceDownload article (715KB PDF).